Study shows greater cancer risk

doi:10.1136/bmj.39450.636875.3A

BMJ 2008;336:59-60 (12 January), doi:10.1136/bmj.39450.636875.3A

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RCGP’s oral contraception study

Study shows greater cancer risk

The first 150 words of the full text of this article appear below.

Hannaford et al reported a significant 12% reduction in therisk of any cancer (adjusted relative risk 0.88, 95% confidenceinterval 0.83 to 0.94), which was widely cited in the popularmedia as reassuring evidence of the safety of oral contraceptives.¹But although it was prudent to exclude participants under age38 at time of loss to follow-up, since use of oral contraceptivesafter that time would be unknown, the authors selectively excludedonly non-users at the time of loss to follow-up.

In their discussion, Hannaford et al report that an analysisof the data with all participants under 38 at time of loss tofollow-up excluded gave a null result (0.95, 0.88 to 1.02).Hence they disproved their own overall result, clearly showingthat their significant overall protective effect of oral contraceptionwas an artefact resulting from the biased exclusion criterion.

Furthermore, they report an increase in breast cancer . . . [Full text of this article]

Joel Brind, professor

¹ Department of Natural Sciences, Baruch College, City University of New York, New York, NY 10010, USA

joelbrind@yahoo.com

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